Disable Mounting of squashfs

An XCCDF Rule

Description

To configure the system to prevent the squashfs kernel module from being loaded, add the following line to the file /etc/modprobe.d/squashfs.conf:

install squashfs /bin/true

To configure the system to prevent the squashfs from being used, add the following line to file /etc/modprobe.d/squashfs.conf:

blacklist squashfs

This effectively prevents usage of this uncommon filesystem. The squashfs filesystem type is a compressed read-only Linux filesystem embedded in small footprint systems (similar to cramfs). A squashfs image can be used without having to first decompress the image.

Rationale

Removing support for unneeded filesystem types reduces the local attack surface of the system.

ID: xccdf_org.ssgproject.content_rule_kernel_module_squashfs_disabled
Severity: Low
References: 11 14 3 9

BAI10.01 BAI10.02 BAI10.03 BAI10.05 DSS05.02 DSS05.05 DSS06.06

3.4.6

4.3.3.5.1 4.3.3.5.2 4.3.3.5.3 4.3.3.5.4 4.3.3.5.5 4.3.3.5.6 4.3.3.5.7 4.3.3.5.8 4.3.3.6.1 4.3.3.6.2 4.3.3.6.3 4.3.3.6.4 4.3.3.6.5 4.3.3.6.6 4.3.3.6.7 4.3.3.6.8 4.3.3.6.9 4.3.3.7.1 4.3.3.7.2 4.3.3.7.3 4.3.3.7.4 4.3.4.3.2 4.3.4.3.3

SR 1.1 SR 1.10 SR 1.11 SR 1.12 SR 1.13 SR 1.2 SR 1.3 SR 1.4 SR 1.5 SR 1.6 SR 1.7 SR 1.8 SR 1.9 SR 2.1 SR 2.2 SR 2.3 SR 2.4 SR 2.5 SR 2.6 SR 2.7 SR 7.6

A.12.1.2 A.12.5.1 A.12.6.2 A.14.2.2 A.14.2.3 A.14.2.4 A.9.1.2

CM-6(a) CM-7(a) CM-7(b)

PR.IP-1 PR.PT-3
Updated: about 1 year ago

- name: Ensure kernel module 'squashfs' is disabled
  lineinfile:
    create: true
    dest: /etc/modprobe.d/squashfs.conf
    regexp: install\s+squashfs
    line: install squashfs /bin/false  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - NIST-800-171-3.4.6
  - NIST-800-53-CM-6(a)
  - NIST-800-53-CM-7(a)
  - NIST-800-53-CM-7(b)
  - disable_strategy
  - kernel_module_squashfs_disabled
  - low_complexity
  - low_severity
  - medium_disruption
  - reboot_required

- name: Ensure kernel module 'squashfs' is blacklisted
  lineinfile:
    create: true
    dest: /etc/modprobe.d/squashfs.conf
    regexp: ^blacklist squashfs$
    line: blacklist squashfs
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - NIST-800-171-3.4.6
  - NIST-800-53-CM-6(a)
  - NIST-800-53-CM-7(a)
  - NIST-800-53-CM-7(b)
  - disable_strategy
  - kernel_module_squashfs_disabled
  - low_complexity
  - low_severity
  - medium_disruption
  - reboot_required

# Remediation is applicable only in certain platforms
if [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ]; then

if LC_ALL=C grep -q -m 1 "^install squashfs" /etc/modprobe.d/squashfs.conf ; then
	
	sed -i 's#^install squashfs.*#install squashfs /bin/true#g' /etc/modprobe.d/squashfs.confelse
	echo -e "\n# Disable per security requirements" >> /etc/modprobe.d/squashfs.conf
	echo "install squashfs /bin/false" >> /etc/modprobe.d/squashfs.conf
fi

if ! LC_ALL=C grep -q -m 1 "^blacklist squashfs$" /etc/modprobe.d/squashfs.conf ; then
	echo "blacklist squashfs" >> /etc/modprobe.d/squashfs.conf
fi

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Disable Mounting of squashfs

Description

Rationale

Remediation - Ansible

Remediation - Shell Script